This invention relates to spin finish compositions for polyester and polyamide yarns, and more particularly to lubricating agents which not only have the properties of reducing fuzz and filament breakage during ultra-high speed texturing of polyester and polyamide yarns and of reducing tackiness of the white powder produced by the false-twisting apparatus but also exhibit highly improved ability to reduce deposits on heaters which are used in the heating processes (hereinafter abbreviated as heater deposit resistance).
In the field of production and manufacturing of polyester and polyamide yarns, there have recently been improvements in productivity due to semi-automation and shortening of work processes. Production of partially oriented yarns (hereinafter abbreviated as POY) and successive or simultaneous draw-false twisting for the production of textured yarn are now being proposed. Faster execution of these processes is also being attempted and this trend is presently growing at a fast rate.
When the speed of these processes is increased, problems and difficulties of new kinds frequently arise and wholly new requirements must be considered for the spin finish to be used in such processes.
Firstly, since the yarn speed increases and so does the contact pressure of the yarns which run against various machine parts such as rollers, guides, heaters and disks, this tends to increase the rate of generating fuzz as well as yarn breakage. For this reason, lubricating agents must now be able to provide higher levels of lubricity and cohesion to feed yarns for false twisting and in particular to those for draw-false twisting.
Secondly, since the yarns run against all kinds of machine parts at high speeds and under high pressures, polymers are physically scraped off and they may accumulate on the friction disks, presenting a significant difficulty from the point of view of work process. Moreover, the tacky white powder thus generated on the friction disks become adhered to the interlacer used for the interlace process on textured yarns. In order to eliminate troubles of this kind, such powder must be prevented from falling off, or the lubricating agent must be such that powder generated would not be sticky.
Thirdly, if there is an increase in the amount of yarns passing through a heater per unit time for heat treatment or in the rotational speed of the yarns, the centrifugal force of the motion will also increase and this will cause all kinds of materials to fall off and scatter around. Since the heaters for heat treatments must be made longer and their surface temperatures raised so that sufficient heat can be supplied to the filaments for setting crimps, this tends to accelerate the thermal degradation of the materials that fall off. If such thermally degraded components (such as tar) accumulate on the surfaces of these heaters, there arise ill effects such as fuzz, breakage of filaments and spotty crimps. For this reason, there now is a great need for lubricants which are capable of preventing materials from falling off and are superior in heater deposit resistance.
Lubricating agents containing various compounds have already been proposed for application in the spinning process so that the subsequent false twisting process can be executed smoothly. As explained above, however, it is found impossible with the conventional lubricants to adequately satisfy the conditions for false twisting which are steadily becoming severer. What is actually being done is, for example, to stop the operation of apparatus now and then so that the surfaces of the heaters can be cleaned. This not only causes a loss in thermal efficiency but also is a backward move away from automation because manpower must be expended for the cleaning work, resulting in reduction in production efficiency. Now that the speed of false twisting process is increasing rapidly, it is indispensable that the lubricant used for this process should stringently satisfy the overall requirements regarding lubricity, cohesion of yarn, non-tackiness of the materials that fall off in the process and antistatic capability.
For improving the heat resistance of a feed yarn in heat treatment processes, it used to be considered important to improve the heat resistance of the lubricant itself and studies have been made of various lubricants which would not themselves undergo thermal degradation or deposit on the heaters. Examples of such lubricants are shown below, but they are unsatisfactory for one reason or another.
Regarding lubricating agents which are to serve as the principal component, mineral oils and esters of aliphatic acids are not desirable from the points of view of fuming characteristics and generation of tar. Esters with quaternary carbon introduced into their molecules (Japanese Patent Tokukai No. Sho 50-53695) and esters of polyoxyalkylenated bisphenol and aliphatic acid (Japanese Patent Tokko No. Sho 53-43239) are fairly resistant against oxidation but since they lack the ability to completely prevent the generation of tar, tar will eventually accumulate as time goes on. Polydimethylsiloxane and its end modified products generate static electricity significantly and lack scouring ability and compatibility with other components of the lubricants (Japanese Patent Tokko No. Sho 58-12391, Tokukai No. Sho 55-67075). As for modified silicones such as methylphenyl polysiloxane and polyepoxysiloxane, they themselves generate insoluble, thermally degraded sludge on the surfaces of the heaters if too much of them (in excess of 10 weight %) is used as components of a lubricant (Japanese Patent Tokukai No. Sho 49-30621 and Tokukai No. Sho 51-67415). Even with polyether-type compounds which are considered to be the most useful lubricating agents among known compounds (Japanese Patent Tokukai No. Sho 56-31077), the problem of heater deposit occurs as explained above under the severe conditions related to the increase in the rate of false twisting process. It has also been pointed out that the rate of deposit may increase even more, depending on the type and amount of emulsifier or anti-static agent added to them. As for the use of .omega.-alkoxy-poly (oxyalkylene) ether derivatives substituting the end hydroxyl group by alkoxy group, etc., (Tokukai No. Sho 54-134198, German Patent No. 1594906), they are too low in molecular weight (less than 1000 with all examples) so that the lubricating agent will fly off the yarns rapidly, causing the amount of oily smoke and tar to increase in the heaters and increasing fuzz and yarn breakage due to insufficient lubrication.
As for constituents other than lubricating agents, addition of a small amount of antioxidant can produce some favorable effects (Japanese Patent Tokko No. Sho 48-17517 and Tokukai No. Sho 53-19500) but it is not suitable under conditions of a high-speed texturing process. Examples whereby a small amount of polydimethylsiloxane, methylphenyl polysiloxane or polyepoxysiloxane (less than about 10 weight %) is added do not show reduction in the rate of generation of tar (Japanese Patent Tokko No. Sho 54-5040 and Tokukai No. Sho 55-137273) and they are generally water-insoluble (even if a large amount is used). Moreover, since these compounds should be emulsified in water as components of the lubricant, the added emulsifier itself will tend to become a source of heater deposit.
As for components other than lubricating agents such as polyalkylene oxide modified polysiloxane, polyethylene oxide modified polysiloxane does not have sufficient heater deposit resistance as a lubricant for feed yarns for high-speed false twisting because the modifying group consists only of an oxyethylene group (Japanese Patent Tokko No. Sho 44-27518). As for the use of a polyether compound in combination with linear organic polysiloxane with kinetic viscosity in excess of 15cst (Japanese Patent Tokukai No. Sho 48-5309), heater deposit resistance has been found to be too small in the case, for example, of methyl (polyethylene oxide)polysiloxane. As for the use of a large amount (over 35 weight %) of polyalkylene oxide modified silicone in combination with polyalkylene oxide with affinity (Japanese Patent Tokukai No. Sho 50-59551), the idea is to reduce the amount of substances dropping from filaments of modified silicone onto the heaters so that an improvement would be made regarding the generation of white sludge on heaters but since, as described above, an increased speed of false twisting or draw-false twisting results in an increase in the centrifugal force on the yarns, it is extremely difficult by a physical means to prevent the lubricant constituents from becoming squeezed out and let fly off the fiber surfaces. As for the method of using polyalkylene oxide modified polysiloxane in combination with a reactive silicone compound in the ratio (former/latter) of 5 to 400/100 in weight (Japanese Patent Tokukai No. Sho 52 -96297), modified polysiloxane itself generates a thermally degraded insoluble sludge on the heater surfaces if it is used as component of the lubricant.